Modern Construction Practice Research Articles

Effect of Proposed Accelerated Curing Method on High Volume Fly Ash Concrete

In the modern construction practice high amounts of fly ash are not accepted by the construction industry due to a slower rate of strength gain at early age. A study has been undertaken to hasten the hydration process by proposed accelerated curing method of high volume fly ash concrete. Large amount of cement (up to 70% by weight) has been replaced by fly ash. The test results of the compressive strength of accelerated cured mixtures gives about (87-100)% strength ratios from itsa28 days compressive strength within one day only. That indicates, the compressive strength at 28 days can be achieved within 1 day only by using proposed accelerated curing. The results of drying shrinkage show that, the drying shrinkage of mixtures under conventional and accelerated curing conditions are comparable and these results add further benefit of this proposed accelerated curing. Key word: accelerated curing, high volume fly ash , curing cycle, drying shrinkage, flow ability.

Qualifying the earthquake resilience of vernacular masonry buildings along the Himalayan arc

Vernacular masonry building types located along the Himalayan arc and incorporating specific earthquake-resilient features have exhibited good seismic performance in past earthquakes. Such buildings are a manifestation of a culture of seismic awareness that developed in these communities over the centuries in response to the local technological, socio-cultural, economic, and environmental contexts. This culture of seismic awareness has eroded in recent years due to socio-economic pressure associated with a desire for modernity of construction. To identify an appropriate balance between traditional and modern construction materials and practices, thereby enabling greater resiliency to the peril of earthquakes in the Himalayas, it is essential to understand the positive and negative attributes of earthquake-resilient vernacular masonry building types. Presented herein is an overview of the identified earthquake-resilient vernacular masonry building types located along the Himalayan arc, as well as an evaluation of the seismic resilient features of these buildings in the context of modern seismic design requirements. The work presented herein shows that earthquake-resilient buildings are feasible when constructed of locally available materials such as stone, mud, and timber, and when using traditional construction techniques, provided that the identified earthquake-resilient features are properly implemented.

Lean Construction and Value Based Approaches for Optimizing Design and Construction Effectiveness in Built Environment Practices

Construction waste remains a critical concern in modern construction processes. Lean construction seeks to provide viable solutions in current sustainability considerations. The paper examined lean construction approaches adoptable in architecture and construction project processes from an integrative approach. The concepts are defined, while attempts are made at explaining its methodological application in the construction process and enlightening on its benefits toward the improvement of modern construction practices. Especially, in the face of constantly evolving challenges and perpetually turbulent environments there is a need to further strengthen seemingly appreciable approaches for achievable resilience.

Учет влияния деформаций шпунтовых ограждений котлованов на дополнительные осадки зданий окружающей застройки

In the practice of modern construction, the development of underground space for buildings and structures erected in dense urban environment is becoming increasingly common. Such construction involves a number of risks, one of which is a significant displacement of excavation enclosures, which in turn leads to additional settlement of the neighboring development. The paper considers some numerical and analytical methods of calculating sheet piling enclosures taking into account both the enclosure displacements and additional settlements of neighboring buildings. The authors propose to improve these calculation methods that can be simplified by developing the empirical-theoretical dependence. The necessary input parameters required for assessing the empirical-theoretical dependence are presented and substantiated, and the method of its construction is described.

ИССЛЕДОВАНИЕ ТЕХНОЛОГИЧЕСКИХ ПАРАМЕТРОВ УСТРОЙСТВА И РЕМОНТА ОСНОВАНИЙ ПЛОСКИХ КРОВЕЛЬНЫХ ПОКРЫТИЙ

In the practice of modern construction, light concretes of low thermal conductivity are used as a thermal insulation layer of enclosing structures. In particular, they are used for insulation of flat roofs of buildings for various purposes. One of their effective methods of thermal insulation is the use of polystyrene concrete of low average density and thermal conductivity directly in building conditions. Studies have established the rational selection of the composition of this type of concrete for the device of a monolithic thermal insulation layer, the resource support of the technological process, including the mechanization of work and qualification requirements for performers. The improvement of organizational and technological solutions of flat roofs based on the choice of rational parameters of technological processes and operations ensures a reduction in the complexity, duration and cost of work on the construction site.

Polymer and non-polymer admixtures for concrete roofs: Thermal and mechanical properties, energy saving and carbon emission mitigation prospective

Buildings are accountable for the enormous energy consumption in the world. Therefore, energy-efficient building materials are inevitable in modern construction practices to diminish global energy consumption. In this paper, three industrial wastes (fly ash, ground granulated blast-furnace slag, and silica fume), four other admixtures (bentonite, metakaolin, oyster shell, and zeolite), and two polymer admixtures (Styrene-butadiene rubber, styrene-acrylic ester) are considered for the concrete to explore their potential for air conditioning cost-savings, carbon mitigations, and payback periods in buildings of hot-dry (Jodhpur, India) and cold climates (Thessaloniki, Greece). The mechanical and thermophysical properties were measured for admixture-based concretes. The results revealed that among all admixtures studied, styrene-acrylic ester concrete roof exhibited better thermal performance with adequate compressive strength (34 MPa). The best economic benefit of styrene acrylic ester concrete roof in hot-dry/cold climatic conditions leading to the highest total air conditioning cost-savings (1.01 $/m2/1.53 $/m2), highest life cycle saving costs (48.9/31.2 $/m2), highest carbon mitigation (19.26/7.53 kg of CO2/year), and acceptable payback periods (11.6/8.4 years). The results of this research help engineers and architects to select the best admixtures for the concrete in terms of mechanical strength, energy efficiency, and carbon emission mitigation potential.

Study on Acoustics in Buildings

Abstract: Acoustics in buildings is that part of science in which importance has been given to the sound quality in building, which enables a proper understanding of the different factors influencing the same. Acoustics being one of the important factor which enables in reduction of transmission of noise and enable a better sound quality in the room. But however either very less or insufficient amount of work has been put in considering the scope of the subject. Some other limitations are builders either do not give priority to that aspect due to lack of information or the improper design and poor implementation. Also The Indian Standard Codes in this area are too old and need updation considering the Modern Scenario and Modern Construction Practices. So efforts have been made to consider this situation and find the best practices, recent innovations and methodologies which could help in maintaining proper Acoustics in Buildings, Halls, Auditorium's etc. And what role could a Civil Engineer play in elimination of this problem. Keywords: Acoustics, Buildings, Material Properties

Interaction peculiarities of a single unit bored pile with the surrounding rock mass under the horizontal load effect

Interaction peculiarities of a single unit bored pile with the surrounding rock mass under the horizontal load effect, as well as loss mechanism of piles bearing capacity, are considered. The article presents the numerical modeling results and a method developed on their basis for calculating piles in rocky soils under the horizontal load effect under the spatial elastic-plastic problem conditions, with the account of the contact behavior between the pile and the rock mass. The study of the single unit bored pile interaction and the surrounding rock mass under the horizontal and moment loads effect was carried out based on the numerical models’ analysis of the piles and the surrounding rock mass in a spatial setting using the finite element method. The use of regression analysis methods made it possible, to obtain parametric equations, based on the numerical modeling obtained results, that connected the studied response functions (bearing capacity and horizontal displacement of the pile) from preselected independent factors reflecting the geomechanical properties of the body and the design piles peculiarities. The developed calculation method allows at the preliminary design stage to estimate the horizontal pile displacement value, as well as its bearing capacity. Also, using the proposed technique, it is possible to make a piles load test schedule, which can be used in the field observation preparation at the design stage. The relevance of the topic is due to the fact that in modern construction practice, bored piles are used to transfer to the foundation significant loads, on the rock foundation from structures for various purposes, including transport (bridges and overpasses piers’ foundations, etc.).

Optimized Design of Cold‐Formed Steel Elements for Serviceability and Ultimate Limit States

AbstractCold‐formed steel (CFS) sections are gaining ever increasing popularity in modern construction practice due to their advantages, such as efficient material use and sustainability. While the manufacturing flexibility of CFS cross‐sectional shapes brings innovative and complex shapes within practical reach, obtaining optimum design solutions can be a challenging task due to the complex mechanical behaviour of CFS elements, which is controlled by local, distortional and global buckling modes, as well as the need to account for manufacturing and end‐use constraints. This study presents a practical framework for the development of optimised CFS beam sections with maximum flexural strength and minimum deflections in ultimate and serviceability limit state conditions, respectively, in accordance with Eurocode 3 (EC3). A population‐based Genetic Algorithm optimisation method is employed to obtain optimum solutions for ten different CFS cross‐section prototypes, while the EC3 geometric restrictions and a number of manufacturing and end‐use constrains are also considered. It is shown that sections optimised based on serviceability limit state (SLS) and ultimate limit state (ULS) requirements can provide up to 44% higher effective stiffness and 55% higher bending moment capacity, respectively, compared to standard commercial lipped channel sections with the same amount of material. The results also indicate that using optimised plain channels and folded‐flange sections generally leads to the best design solution in SLS and ULS optimization, respectively.

Evaluation of Compressive Strength of Sustainable Concrete Using Genetic Algorithm Assisted Artificial Neural Networks

Sustainable concrete which contains fly ash and slag is increasingly used in modern construction practices. This study presents a genetic algorithm (GA) assisted artificial neural network (ANN) model for evaluating the compressive strength of sustainable concrete. 425 mixtures are used for making the prediction system. Genetic algorithm (GA) is used to generate the initial values of the weight matrix and bias of ANN. The input parameter of GA assisted ANN is water-to-binder ratio, fly ash or slag replacement ratio, sand ratio, and water contents. The output result is compressive strength. The correlation coefficients for single ANN and GA assisted ANN model are 0.88 and 0.911, respectively. GA assisted ANN model has a strong prediction ability for the strength of sustainable concrete.

The Possibility of Using the Ultra-Thin Liquid Thermal Insulation to Insulate the Ceiling above the Basement in Residential Buildings

The issues of energy saving, as well as comfortable operation of buildings in modern construction practice are relevant. The experience of operation of the premises, located above the basement, shows that the most common problem is the cooling of the floor slab and, as a consequence, the presence of a cold floor. The article presents the results of calculations on the change of thermal properties of the ceiling above the basement in residential buildings. A variant of insulation of the ceiling with ultra-thin liquid insulation is proposed. The graphical analysis of the problem is carried. As a result of graphical analysis, it was revealed that the proposed method of insulation makes it possible to increase the floor temperature in the rooms of the ground floor in the residential buildings.

Geometric and physio-mechanical characteristics of the contact layer area of multilayer reinforced concrete structures

In the practice of modern construction, multi-layer building envelopes made of concrete of various physio-mechanical characteristics has been wide applied. During successive layer-by-layer laying of various concretes, contact layers are formed between them, and their physical and mechanical characteristics are different from the adjacent layers. Technological and time factors for the manufacture of this structure affect the formation, physical and mechanical characteristics of the contact layer between the inner and outer structural layers, and effecting to the working of the multi-layer structure. In this article, the geometric and physio-mechanical characteristics of the contact layer zone of multi-layer reinforced concrete structures are researched. The main content of study was conducted on samples of three-layer structural blocks with using strong structural concrete B25 in the external layers, and low-strength concrete in the middle layer. The geometric and physio-mechanical characteristics of the contact layers were researched by the experimental method. Based on the results of experiments, the geometric and physio-mechanical characteristics of the contact layer of multilayer reinforced concrete structures are shown, taking into account the influence of technological and time factors for the manufacture of this structure. Moreover, the results of the study allow us to determine rational parameters in design of multilayer envelopes with reinforced concrete layers of various strengths, interconnected by a monolithic contact layer. According to the results, modification and calculation method for multilayer reinforced concrete building envelopes has been evaluated and applied into the production process of these constructions.

Criteria for climatic applicability of modern window types

Currently, the assignment of the required values of the technical and operational windows characteristics (such as resistance to heat transfer, air permeability, sound insulation, etc.) is carried out based on the technological capabilities of the window industry, and not on the basis of scientifically substantiated requirements for ensuring the microclimate and energy buildings efficiency in the design practice of most countries (as it happens in the case of external walls which are in almost identical operating conditions with windows, for example). One of the most common types of windows in modern construction practice are single windows with insulated glass units and profiles made of PVC and aluminum alloys. They were originally developed for operation in Western Europe where they have proven themselves well over many years of operation. However, their widespread use in the climatic conditions of the Russian Federation and the countries of Eastern Europe showed a number of problems during operation which is expressed in a decrease in the technical and operational characteristics of windows due to temperature deformations of their profile elements. This circumstance testifies to the limited area of application of these structures in terms of climatic conditions. The authors of the work introduce the concept of “climatic applicability of windows” in order to determine the rational application areas of types of windows which would ensure the fulfillment of the specified requirements for the comfort of the microclimate of the premises in any operation period of the building. Based on the results of the analysis of the work of third-party researchers and the authors own works the authors have determined a set of criteria for the climatic applicability of modern types of windows based on winter operating conditions. Promising areas for further research were considered.

Experimental and Analytical Studies on Harden Properties of Cement Composite Using Different Fibres

Cement composites are the most used composites in the world. In modern day construction practice, repair and rehabilitation of structures has taken an important role. The brittleness of cement composites can be reduced by reinforcing it with fibres for better shear and flexural behaviour of composites. This research work targets n experimental and analytical evaluation of the mechanical properties of fibre reinforced cement-sand composites. The effect of fibres on Compressive strength, Shear Strength and flexural strength were analysed. According to the results of this study, certain amount of fibres enhances the mechanical properties of the fibre reinforced cement-sand composites.

Assessment of the effect nitrites and fluorides on the change in the strength of concrete

The article describes examples of using inorganic salts and their mixtures for accelerate of hardening cement concretes in practice of modern construction. The results of the research of a complex mixed additive based on inorganic fluorides and nitrites, which accelerate the process of hardening of cement concrete are presented. The composition of the additive allows to accelerate the process of hardening the cement stone, due to the formation of dense and insoluble compounds in the pores of the cement stone. The experimental part included the process of determining the optimal amount of fluorides and nitrites in the additive. The results of the research showed a reduced additive consumption per 1m3 of heavy concrete. The advantages and disadvantages of the additive, which identified at experiments, allow us to recommend its use for accelerating the hardening of concrete in wet neutral and slightly acidic environments. The methods of tests that were carried out using certified and calibrated measuring instruments are described in detail. According to the results of the tests, the dependence of the concrete hardening rate on the amount of additive used was revealed, and the ways of practical use of the additive in the production technology of concrete and reinforced concrete were proposed. Also, according to the results of destructive and non-destructive testing, an increase in the strength of concrete by >15% compared to conventional concrete was found.

Determination of physico-mechanical characteristics of concrete for 3D printing building designs

Problem statement. Currently, methods of manufacturing building structures and products using a 3D printer are becoming increasingly popular. In 3D printing technology one of the main factors that affects the quality of the final product is the composition of the concrete mix used. Moreover, for each type of product, it is important to develop a separate composition of the mixture, which has certain physical and mechanical properties. Analysis of the current state of development and research of concrete for 3D printing of structures showed that the choice of materials for printing depends on the functional purpose of the created object and its scope. At the same time, a distinctive feature of concrete used in the practice of modern construction is that each developer of a 3D printer presents its mixture without revealing its composition. Analysis of publications. The main material used in 3D-construction is concrete-an artificial stone building material obtained as a result of the formation and solidification of a rationally selected and compacted mixture. Such a mixture consists of a binder-cement, large and small aggregates, water, and in some cases with the addition of various modifying additives. One of the main directions of modification of concrete mix is the use of special additives, which significantly affect the characteristics of concrete. Examples of such additives are kaolin clay, silica fume, air lime, fly ash, superplasticizers, hardening accelerators, and mixture strength set. In world practice, for 3D printing of structures for concrete reinforcement, a variety of fibers, fiberglass and other fillers are introduced into the mixture, which can significantly increase the strength of concrete. Currently, in Dnipropetrovsk region in Bratskoe village there is a production room, where the production of small piece concrete products with the help of 3D printing has been established. Department of Reinforced Concrete and Masonry Structures, State Higher Education Institution “Pridniprovska State Academy of Civil Engineering and Architecture” established cooperation with this production facility, engaged in the improvement of manufacturing technology and the application of mixtures, as well as the development of optimal concrete compositions. The first step of such cooperation is the development of mixtures with various binders and hardening accelerators, which significantly affect the reduction of the setting time of mixtures. Purpose of the work was to identify physico-mechanical characteristics of concrete,which is used to manufacture the structures at the production plant in Bratskoe. At the same time the goal was also to compare the characteristics of concrete made using 3D printing by extruding the mixture through a nozzle and molded by manually sealing the mixture. Conclusions. It is found out that in modern construction it is quite efficient and technologically simple to implement the advantages of 3D printing technology for the manufacture of individual structural elements of buildings and structures. As a result of tests of concrete compositions for 3D printing of structures, it was found that the closest concrete grade in terms of strength of basic samples-cubes that were made in molds is M300, and samples-cubes that were selected from structures is M250. Scale factors were established for the samples-cubes with ribs of 100, 70, and 50 mm, which were determined with respect to the strength of standard specimens with a 150-mm rib size.

Development of software complex for calculating stability of industrial buildings located near the slopes of industrial buildings during their reconstruction

Problem statement. In cities, there is a significant shortage of territories suitable for construction, which leads to the need to design buildings in difficult conditions − to carry out development for the construction of territories that were previously considered to be unsuitable, it is increasingly necessary to construct buildings on unstable slopes, to carry out construction of projects in former industrial areas after changing functional purpose. Therefore, the issue of rational design and construction on unstable slopes is relevant. Purpose of the article. Development of a software complex with the help of which it would be possible to carry out calculations by the most common classical methods: stability of slopes without and with reinforcement, stability of buildings located next to slopes, determine the pressure of one block of soil mass on another, soil pressure on holding structures, determine the stability of slopes in the presence of a filtration stream, in the presence of wave pressure. Conclusion. As a result, a software package was developed that makes it possible to carry out stability calculations using the methods of Yu.I. Soloviov, K. Tertsahi, Maslov-Berer (“classical” and “hydrostatic”), H.M. Shakhuniants, A. Dorfman, when designing new and reconstructing existing industrial buildings located near slopes. The program enables these methods to perform slope stability calculations; structures located on the slopes; take into account the effect of reinforcing slopes; calculate the stability coefficients of reinforced slopes: when the reinforcing layer breaks, when the contact strength between the reinforcement and the soil is lost, when the reinforcing layer breaks and the contact strength between the reinforcement and the soil is lost; calculate the influence of the filtration flow in the presence of wave action in calculating the slope stability. All this makes it possible to use widely this software package in modern construction practice.

PORTABLE HEAT METERING SYSTEM DESIGN

In modern construction practice, more than half of buildings in operation require modernization of thermal insulation. However, in order to select an effective insulation system, it is necessary to know the actual thermal and technical characteristics of structures and parameters of the building internal environment. The paper analyzes methods and equipment for evaluation of the thermal performance of outdoor enclosures. The advantages and disadvantages of the main devices recommended by the regulatory documents for field research are shown. According to the data obtained, a heat engineering complex is developed for conducting field studies of heat and humidity of wall structures and microclimate of building premises. Software improvement together with Arduino reader device allow monitoring both at stationary and non-stationary thermal conditions of external enclosures and indoor climate parameters in field conditions.

Development and Research of Properties Cement Concrete Hardening Accelerator Additive Based on a Mixture of Inorganic Fluorine-Containing Salts

the article describes the basic salts and their mixtures used to accelerate the hardening process of cement concretes in the practice of modern construction. Development and main characteristics of the additive accelerating process of hardening of cement concrete are presented. This additive is based on a mixture of non-organic fluorinated salts. The composition of the additive allows to accelerate the process of hardening of cement stone, due to the formation of insoluble and dense compounds. A number of experiments were carried out to determine the optimal amount of fluoride salts in the additive. The results of the research showed a low consumption of additive per 1 m3 of heavy concrete. Advantages and disadvantages of the additive allow us to recommend its use to accelerate the hardening of concrete in a wet environment. The article provides a detailed description of the test methods. The tests were carried out using certified and verified measuring instruments taking into account the strength characteristics of the materials. As a result, the dependence of the concrete hardening rate on the amount of additive used was revealed. The article also discusses some proposals for the practical use of additive in the production technology of concrete and reinforced concrete. According to the results of destructive and non-destructive testing, an increase in the strength of concrete by >30% compared to conventional concrete.

Energy Efficient Technologies for the Construction and Buildings Reconstruction

All The integrated approach features to the application of energy-efficient technologies in the buildings and structures reconstruction and construction, which is accompanied by rigorous research, preparation and testing of experimental energy-efficient objects and samples with their further introduction into modern architectural solutions and construction practices are considered. Unlike energy conservation, energy efficiency in construction is aimed at using less energy to satisfy the same level of buildings energy supply or technological processes in production. It is shown that for a qualitative assessment of the improving the energy efficiency of buildings and structures possibility, all areas of energy loss should be assessed. Therefore, priority in technology should be put on improving the thermal insulation efficiency, mounting recovery devices to use exhaust air heat, and also include measures to prevent the warm air infiltration through windows, doors, balconies, and indoors to use instruments to control their internal temperature. Improving energy efficiency should be attributed to the strategic objectives of the state, being at the same time the main method of ensuring energy security.